1. Field of the Invention
The present invention generally relates to double-sided UV exposure systems for printed circuit board manufacturing and more particularly to a four post phototool die set incorporating all actuation elements below the exposure plane to avoid particulate contamination of art work or work pieces within the exposure chamber.
2. Description of the Prior Art
Double-sided exposure systems for printed circuit boards have been developed employing motorized systems for photo tool die set operation, art work alignment and die alignment. U.S. Pat. No. 5,337,151 entitled Double-sided CIRCUIT BOARD EXPOSURE MACHINE AND METHOD WITH OPTICAL REGISTRATION AND MATERIAL VARIATION COMPENSATION assigned to Optical Radiation Corporation, the assignee of the present application, discloses an integrated system for double-sided circuit board exposure.
The requirements for increasing precision in the processing of printed circuit boards for alignment of art works and work pieces as well as maintaining cleanliness of the photo exposure environment continue to increase as additional reduction in lead pitch and density for PCB applications occurs. A need therefore exists for double-sided exposure systems maintaining high accuracy, speed and smooth operation while conforming to clean room design principles. Such systems however, must preferably accommodate automated work piece transport and handling systems available on current exposure devices.